Carl Sagan

A candid conversation about heaven and earth and all the ozone in between with the most influential space scientist in the cosmos

Billions and billions of years ago (about 15, give or take a few billion), the universe, in its present incarnation, was formed. To get a sense of how recently humans came onto the scene, imagine the history of the universe condensed into a single year. If the Big Bang that likely started it all was on New Year’s Day, the Milky Way originated on May Day and the solar system on September ninth. Earth didn’t show up until mid-September and, around November 15–hallelujah–the first living cells with nuclei came to be.

December was a big month on the green planet: Worms appeared on the 16th, fish a few days later; dinosaurs joined the group on Christmas Day and, the day after that, mammals. Humans, however, didn’t appear until the last day of the year, December 31, and then not until 10:30 P.M. Stuffed into the last hour and a half was the history of man: Buddha was born at 11:59:55, Christ a hundredth of a second later. The Renaissance took place between 11:59:58 and 11:59:59. Then, a fraction of a second later, just as the champagne cork was about to be popped, the man who came up with this engaging stellar calendar was born. His name was Carl Sagan.

Since that time, Sagan has become one of the best-known space scientists, astronomers and environmentalists in the world–a man lauded not only for a solid body of scientific work but also for an ability to make complex science palatable, even enthralling, to the rest of us. Instead of talking ring occultation and radiative-convective models, Sagan tells stories. “To make an apple pie, you need wheat, apples, a pinch of this and that and the heat of the oven,” he writes on “The Lives of the Stars” in his book Cosmos. “The ingredients are made of molecules–sugar, say, or water. The molecules, in turn, are made of atoms…. A star is a kind of cosmic kitchen inside which atoms of hydrogen are cooked into heavier atoms…. If you wish to make an apple pie from scratch, you must first invent the universe.”

Sagan’s science reached its huge audience through his books, many of which (including the Pulitzer Prize-winning The Dragons of Eden) have been best sellers. But it was television that propelled Sagan to superstardom–most notably, public TV’s adaptation of Cosmos, whose initial three-year run was seen by 400,000,000 people in 60 countries. (The program has since been rerun on TV and released on video.) Not unlike most cultural icons, Sagan has also earned his share of dubious honors; specifically, the distinction of being made fun of more than any other scientist in history. While shows such as Saturday Night Live have taken their shots, the Tonight Show’s Johnny Carson is credited with the definitive lampoon: Donning a wig and a corduroy jacket, he folds his arms across his chest and intones, in a voice trapped somewhere in his sinuses, “Billions and billions of years ago….”

Well before he became fodder for comedy writers, Sagan was at the forefront of space-science research. He worked on Government space-advisory committees and, after NASA was formed, began participating in its unmanned space projects. His more esoteric research during those years included a ground-breaking report on the structure of Venus’ lower atmosphere and a study that explained the nature of Mars’s seasonal changes and dusty surface. He has since been involved in research projects related to most space flights, particularly to the unmanned Mariner, Viking and Voyager interplanetary expeditions. For the Pioneer and Voyager missions, Sagan was asked to create interstellar records–visual and aural messages about earth that were intended for any intelligent beings who might stumble upon them in the far reaches of space.

Sagan has collected dozens of awards (including NASA’s medals for Exceptional Scientific Achievement and for Distinguished Public Service), belongs to 24 scientific societies and has 18 honorary doctoral degrees. But he is viewed by some scientists and critics with suspicion, even scorn. (A journalist once claimed Sagan was interested “more in Sagan than in science.”) Clashes with Sagan have most often taken place on the battlefield of politics; his outspoken candor covers issues from nuclear weapons to abortion. He has come out against not only Star Wars but also against the space shuttle and the space station; he openly campaigns for political candidates–he was even arrested while protesting nuclear testing in Nevada.

More recently, Sagan has been at the center of another storm. In A Path Where No Man Thought, a book published last year, Sagan and atmospheric-scientist Richard Turco outlined their controversial nuclear-winter theory. They claim that a limited nuclear war could do far more damage to earth than has been previously imagined, turning it into a “dark, cold, soot-covered world.” For their work, the two received the American Physical Society’s Leo Szilard Award for Physics in the Public Interest. The theory was vehemently attacked in conservative circles as being more about politics than about science.

Despite the discord, Sagan continues to be a favorite source on matters scientific. He has testified before Congress, Presidents and the Department of Defense on many issues, including his nuclear-winter theory; when “Nightline” needs an expert on the Kuwaiti oil-well fires, Sagan is called; he writes articles for newspapers and magazines on why we should teach our children more about science and why there should be a joint U.S.-Soviet mission to Mars.

That last issue–going to Mars and other planets–is not a new one for Sagan. He has dreamed about it since he was a child. Born in Brooklyn on November 9, 1934, he was the son of a Russian immigrant who worked as a theater usher, then a garment cutter. At the age of five, Sagan recalls, he looked into the heavens, spotted the stars and wanted to know about them; by the time he was eight, he was determined to visit the planets; and as soon as he learned that there was such a thing as an astronomer, he decided to become one.

Graduating from high school and enrolling at the University of Chicago, Sagan earned a doctorate in astronomy and astrophysics. He taught at Berkeley, Harvard and Stanford before being appointed to his current position as director of the Laboratory for Planetary Studies and professor of astronomy and space sciences at Cornell University.

Sagan is married to Ann Druyan, novelist, television writer, producer and an officer and a trustee of the Federation of American Scientists–an organization concerned with the responsible use of science. Druyan was also creative director of a “sound essay” placed aboard a Voyager spacecraft. Together, the couple have worked on various projects, including TV’s Cosmos–she wrote several episodes–and a novel, which is being made into a feature film. The two, who recently had their second child (Sagan has three other children from two previous marriages), are currently at work on a trilogy of books. The first installment is Shadows of Forgotten Ancestors: The Earth Before Humans.

While Sagan’s stellar calendar puts us at the brink of a new year, our calendar says that we are fast approaching a new century. As issues of technology, space and the environment continue to confront the human race with increasing urgency, we decided it was time to press America’s reigning space scientist for some answers to the big questions. To interview Carl Sagan, we picked Contributing Editor David Sheff, who had just returned from his interview with globe-trotting media baron Robert Maxwell. Here is Sheff’s report:

“Sagan lives on the outskirts of Ithaca, New York, home of Cornell, in an impressively large yet comfortable wood-and-glass home amid a forest of pine, oak and an abundance of wildflowers.

“When he greeted me for our first interview session, he was holding his youngest child, Sam, who was only a few months old. We sat in the living room in the middle of a charming familial scene: Since Mom was out shopping. Dad fed Sam a bottle while nine-year-old Alex ate sticky cotton candy and played on the floor near us–all while Dad waxed eloquent about meteor-burst communications.

“The second time I showed up in Ithaca, Sagan was disheveled, his dark hair fighting against whatever brushing had occurred that morning. He also needed a shave. When it was time for lunch, he pulled on an old leather jacket and suggested that we head to the faculty club at Cornell. Although he once drove an orange Porsche with a license plate that read Phobos (his favorite Martian moon), we rode to Cornell in his current car, the far more ecologically friendly VW Rabbit.

“Between our meetings, I had been in Kyoto, Japan, at an international conference of scientists. The subject was relativity and the keynote speaker was Stephen Hawking. There were days and nights of workshops about basic theories of creation, matter and time.

“Sagan didn’t attend, but he was nonetheless a topic of conversation among a group of astronomers and physicists at the sushi bar in the lobby of the hotel. ‘Look,’ one of them said, ‘Sagan is simply wrong half the time he says anything. There are holes everywhere.’

“A colleague interrupted. ‘You just don’t like it because it’s Sagan,’ he said. ‘You’re jealous.’

“The first scientist shook his head. ‘No, but it does irk me that he is always in the middle of everything, everywhere you look. Besides,’ he added, ‘what’s he got that I haven’t got?’ The crowd began laughing when he broke into an impression that was even better than Carson’s: ‘Billions and billions of years ago….’

“Although my conversations with Sagan would eventually delve into the great mysteries of the universe, I decided to begin with a question that more or less cut to the chase.”

Playboy: What don’t you understand?

Sagan: Almost everything. Seriously. There are lots and lots of people who understand things better than I do, but there is no one on the planet who understands any issue perfectly. There’s always a place where human limitations come in and we just don’t understand anymore.

Since I have difficulty understanding many things, I have to go through a certain internal procedure. As far as I can see it, my only secret in being able to talk to others about science is to remember what it was like when I didn’t understand whatever it was we were talking about.

Playboy: Most scientists spend their time in research labs. Was there a single experience that made you want to communicate science?

Sagan: I would speak at a scientific meeting and a reporter would talk to me afterward to ask about the work I was discussing. I guess I did OK explaining things, because people would come back to me. Then I would be invited to television talk shows. Johnny Carson saw me on one and invited me onto his show. That was about the time that a popular book of mine called The Cosmic Connection came out. Also, the BBC asked me to host some science programs and things just sort of snowballed. I found that people were interested and they knew a lot. Carson himself, I discovered, was truly interested in science; he has real knowledge of astronomy. At the same time, of course, he’ll take the heat shield from my model of the Viking spacecraft, put it on his head and start talking Martian.

Playboy: Thanks to Carson, you’ll never live down your line “Billions and billions of years ago….”

Sagan: The oddest part is that I never said “billions and billions.” Then again, Humphrey Bogart never said his most famous line, “Play it again, Sam,” and in the books, Sherlock Holmes never said, “Elementary, my dear Watson.”

Playboy: Why is there often contempt within the scientific community for the idea of popularizing science?

Sagan: In about five hundred B.C., the Pythagoreans discovered that the square root of two is an irrational number. You can’t represent irrational numbers as the ratio of two numbers, no matter how big those numbers are. This was considered to be such dangerous information that it was classified. No ordinary person was permitted to know this.

Playboy: Why?

Sagan: No one knows. For whatever reason, it was considered dangerous. You can find examples all through history of this insulting attitude: that the public cannot be trusted with knowledge. Nowadays, some scientists justify that stand by saying it’s impossible to communicate such knowledge accurately; you always have to simplify things because, in essence, the public is too stupid. But the dumbest thing scientists who depend on public funds can do is not tell the public what they’re using the money for. It’s suicidal. I think those attitudes are declining swiftly and there are lots of scientists who do an excellent job of explaining things. They convey a sense of excitement, a sense that science is worth while.

Playboy: Why do you do it?

Sagan: Because the chance to talk to millions of people–probably very few of whom subscribe to Scientific American, yet are still interested in science–is too good to pass up. Scientists who can get people excited about the field serve as role models for youngsters. Beyond that, if you’re in love with something, then there is a natural tendency to want to tell people about it. And we must! If people who disseminate information think their audiences are too stupid to understand science concepts, they’ll never let them have any real science. It’s a small thing, but Hollywood movies in which science is somehow involved in the plot almost always get it wrong. Why don’t they just hire a graduate student to check it?

Playboy: Give us an example?

Sagan: In Star Wars, a movie I greatly admire, the term parsec, which is a unit of distance, is used as a unit of time or velocity. Why not get it right?

Playboy: Probably because some people consider the science part unimportant.

Sagan: People are intimidated. The idea that they aren’t interested is nonsense. Cosmos shows us that they’re interested. It is one of the most-watched public-TV shows ever. The accompanying book is also one of the most widely read science books ever published in the English language. Yet parents and even teachers freeze up when their kids ask them simple scientific questions: Why is the sky blue? Why is the sun yellow? What’s a dream?

Look at Mr. Bush! On several occasions, he has said that he can’t understand anything about science, as if he were proud of it. I don’t think that’s something to be proud of. It’s a sign of a nation that doesn’t care about it’s future. Every newspaper in America has a daily astrology column. How many even have a weekly science column?

Playboy: What is the interest in astrology and other pseudosciences all about?

Sagan: The contentions are interesting, even flattering. “The motion of the stars is connected with my character? Boy, I must be really important!” If ghosts exist, then my loved ones who have died are not really dead. Personally, I would love to believe I could make contact with my parents, whom I miss terribly. But I recognize that I’m vulnerable for just that reason, and so I demand rigorous standards of evidence in such a case. Whenever there is a dearth of science, people will fall for all that stuff.

There was a notion in the Sixties and Seventies that monumental structures world wide–the Pyramids, the city of Great Zimbabwe, the Easter Island megaliths, straight lines in the plains of Nasca in Peru–were built by occupants of UFOs who visited earth in the past. The proof for the theory was fundamentally that our ancestors were too stupid to build big. All of this is a mixture of genuine intellectual interest and the absence of any countervailing examples of skeptical thinking.

Playboy: So you’re saying that the Egyptians, not aliens, did, in fact, build the Pyramids?

Sagan: It’s fundamentally naive to look at the Pyramids, see that they’re really big and then conclude, “I couldn’t even lift those stone blocks with my friends helping; therefore, aliens had to do it.”

Playboy: What about the Bermuda Triangle? How do you explain that?

Sagan: Statistically, it’s a fallacy. Compared with other places in the world as well traveled as that area of the Atlantic, do airplanes and ships go down more? The answer is no. Why is it always planes and ships that get lost? It’s because they can sink in water. If we started losing trains–if we had a Duluth Triangle in which trains began disappearing–that would be interesting.

Playboy: Your skepticism doesn’t keep you from believing there’s life on other planets?

Sagan: It seems to me very likely that the galaxy is brimming with intelligent life, but that doesn’t mean I know that that’s the case. And it sure doesn’t mean that I know that we’ve been visited.

Playboy: But, in a sense, extraterrestrials are no different from astrology, crystals or channeling: They represent people’s longing for something more than just the here and now.

Sagan: The difference is the statistical likelihood that in the universe, there is more life than ours. There is so much organic matter, so many worlds, and billions of years of evolutionary time; why should we be the only life to have developed? But I don’t know. The only way to know is to look.

Playboy: You’ve even tried to communicate with extraterrestrial life by creating messages that have been sent into space.

Sagan: The human species has launched four spacecraft to the stars. After they finish doing their jobs of exploring the outer solar system, they leave it and just wander in the dark, essentially forever. For the first two spacecraft, Pioneers ten and eleven, my colleague Frank Drake and I designed a plaque–essentially, a license plate–that is affixed to one of the supports. It shows a naked man and woman, some scientific hieroglyphics of our solar system, information about when we launched the craft, a model of DNA–a few things like that.

Playboy: Doesn’t the plaque presuppose that a being able to decipher this would have an awful lot in common with us?

Sagan: Sure. But remember, the being would have to intercept a spacecraft whose transmitter had long before failed in the depths of interstellar space–and that’s a capability far beyond our own. So they would have to be much further advanced than we.

Playboy: Then, with the Voyagers, you sent audio messages.

Sagan: Right. By then, the technology had come along, so we didn’t have to do a license plate. Instead, we made a sort of phonograph record.

Playboy: Which assumes that the aliens have a stereo.

Sagan: Again, if they can find the spacecraft, they can understand the message. The laws of science are the same throughout the universe.

Playboy: What’s on the record?

Sagan: First, it has greetings in sixty human languages–not that we expect extraterrestrials to know any of them, but it seemed dumb not to say hello. Then, there is a sound essay that includes everything from the mud pots of primeval earth to the launch of a rocket to the sound of a kiss. There are also a hundred and seventeen digitally coded pictures that include information about our civilization, science, the planet and ourselves, and then an hour and a half of the world’s great music–from east and west.

Playboy: For instance?

Sagan: Some Louis Armstrong, Blind Willie Johnson, a Bach partita, the Queen of the Night aria from Mozart’s The Magic Flute, gamelan music, Japanese shakuhachi music, native American music, Australian aboriginal music. We tried to get the Beatles’ Here Comes the Sun, which we thought appropriate. All four Beatles gave permission, but they didn’t own the rights, and the record company said no. They were afraid of extraterrestrial competition or something. We used Johnny B. Goode.

Although the messages are certainly intended for out there, more importantly, they’re intended for down here–to help us to think of ourselves in a cosmic context.

Playboy: You’re now pushing for a joint U.S.-Soviet program to Mars. What are we looking for there?

Sagan: There’s so much to look at. Mars was once an earthlike world; today it is in some deep ice age. What happened? I want to know how an earthlike world gets into a permanent ice age. It seems to me there are practical reasons we should understand that.

Playboy: How earthlike was Mars?

Sagan: There were rivers, running water. There may have been oceans. But how deep do you dig before you get to some remnant of that ancient environment?

Playboy: Why are you pushing for a joint program rather than one for just the U.S.?

Sagan: To save money and get many countries involved in one incredible joint adventure. Beyond that, and in the long term, this could be a step toward humans’ settling on other planets. It is as major a step as when our simian ancestors came down from the trees and into the savannas, and as important as when our amphibian ancestors first settled the land five hundred million years ago. The historical importance cannot be overstressed. This is a long way off. I’d love to see it done in my lifetime.

Playboy: Since we’re not working with the Soviets, will there be a new space race against them?

Sagan: No. They’ve won.

Playboy: They’ve won?

Sagan: We won it to the moon, the Soviets won it to space stations in low earth orbit. So now we need to work together. Except for considerations of national pride, there’s no reason not to do it. I think there is a real chance that we will see, before this interview is published, an announcement about U.S. astronauts on Mir, the Soviet space station, and Soviet cosmonauts on the shuttle. The logic is so clear and the money is so short that it is in the best interest of both nations to cooperate.

Playboy: Still, both countries are facing some hard economic times….

Sagan: Right, and what I find galling is this: Why, then, are both countries spending so much money on defense?

Playboy: But it’s not just defense. How can you justify spending money on space research and exploration when there are so many issues we have to face closer to home? Shouldn’t we first feed people, conquer AIDS and cancer?

Sagan: But if you cut basic scientific research down here, you’re eating the seed corn. You’ve got a little bit of corn to get you through the winter, but then you’ll have nothing to plant. And the economies of the United States and even the Soviet Union are big enough that it’s possible to spend money on short-term and long-term objectives. We have to do both. What would you say to someone who said, “Let’s close all the schools in America. Think of the money we can save”? Everybody recognizes that, while you might gain something in the short term, in the long term, it’s catastrophic.

Playboy: But why does our country allocate money for the space program when our budget is such a mess?

Sagan: There are so many reasons: communications satellites; weather satellites, which save billions of dollars in crops every year; and military reconnaissance, surveillance and treaty-verification satellites, which calm the hotheads and paranoids on all sides. If the space program did nothing more than those three things, you would still have to support it.

But there’s lots more. Scientific satellites, starting with those that orbit the earth and monitor the environmental health of the globe. And what we learn about our environment from spacecraft that explore other planets is worth the entire investment of the space program.

Playboy: Such as?

Sagan: If anybody doubts that a big carbon-dioxide greenhouse effect can be dangerous, look at Venus. Nine hundred degrees Fahrenheit! Now tell me that the greenhouse effect is just made up by liberal college professors!

See, exploration of all those other planets, searching for life elsewhere, is as essential as anything. It helps us understand how our world came to be and where it may be going. We have the earth-orbital satellites with large telescopes looking into the depths of space—-

Playboy: Such as the Hubble telescope, with its myopic lens.

Sagan: Well, Hubble is an embarrassing example, though the lens is fixable with a correcting lens, like an eyeglass. And it will be corrected. But in spite of the problem, Hubble has already trotted out dozens of important new discoveries, and it’s just starting. When the correcting optic is sent up–which, by the way, is the size of a silver dollar–it will be invaluable. And the over-all point: The military budget is three hundred billion dollars a year, Persian Gulf excluded. The space program’s entire budget is fourteen billion dollars.

Playboy: In general, does NASA spend its money well? Is the Hubble mistake an exception or the rule?

Sagan: For many years, NASA was perceived to be–and, to some extent, was–a group of wonder workers. All through human history, people looked up at the moon. And then we got there. What a mythic accomplishment! It would be foolish to forget the historic accomplishments of NASA just because it launched a nearsighted telescope. But without the kind of Presidential attention that it got in the Kennedy and Johnson years, NASA has sort of dwindled. It has been forced to find its own justifications.

Playboy: How did the Challenger disaster affect the country’s attitude toward space exploration?

Sagan: It certainly did call into question NASA’s invulnerability, which was a myth, anyway: The Apollo One fire lost astronauts well before Challenger. But after Challenger, a lot of people had the sense that we had to go back with a redoubled effort in order to make sure the loss of those brave astronauts was not in vain. You could argue that it helped pump up the program.

Playboy: Was the Challenger disaster bound to happen?

Sagan: If you believe some of the statistics they gave us after the fact, it was exactly when you would expect a disaster. But one of the NASA contractors that built the shuttle said you would have to wait ten thousand years before there would be such a disaster.

Playboy: Where were you when it happened?

Sagan: I was flying to Tel Aviv. I got off the airplane and the press was waiting there to ask me about it. I was devastated.

Playboy: How does the current Administration’s less-than-vigorous support of the program affect the program itself?

Sagan: The shuttle is an attempt at bureaucratic self-maintenance.

Playboy: You obviously disapprove of the program. Why?

Sagan: When the Apollo program ended, there was no long-term goal for NASA; it had to invent a goal, and the shuttle was it. But, mostly, there is no reason for the shuttle. For example, the objective of the Challenger mission, which killed seven brave Americans, was to launch a communications satellite. But we’ve been launching communications satellites for decades with unmanned rockets that don’t risk people’s lives.

Playboy: NASA says we need the shuttle to construct and maintain its proposed space station, Freedom.

Sagan: But why do we need the space station? One answer: because the shuttle has to do something.

Playboy: We would imagine you to be a staunch supporter of the space station.

Sagan: What is it good for?

Playboy: For starters, isn’t it a fairly exciting science lab in space?

Sagan: For what? For observing the earth or the stars? No, because you do that with the robot satellites. So what is it for? For manufacturing in gravity-free environments? That was an original argument–you could make pharmaceuticals, cure cancer, make ball bearings–but you could tell very early that that was a fantasy. Essentially, no American corporation was willing to spend significant money on the space station as a place to do its manufacturing. You don’t hear much these days about space industrial parks.

Playboy: When has sending people into space been merited?

Sagan: Since Apollo, manned missions have not been essential. They haven’t done a thing, in my view, except learn a little about humans in space.

Playboy: But there are things a robot cannot do; it can’t think in a crisis, for one important example.

Sagan: It can make most decisions on its own, and if it doesn’t have an answer, it can always send questions back to earth. Voyager, which was Seventies technology, had to fix itself mid-mission many times.

Playboy: Do you see any merit in sending people into space just for the sake of it–as in the Star Trek motto, “To boldly go where no man has gone before”?

Sagan: Certainly–if we were going to other worlds. If we had a spacecraft like the Enterprise on Star Trek–with men and women aboard who could go anywhere–boy, I’d be signing up myself. But what we’re talking about is spending an enormous amount of money to make something we don’t really need. The manned–peopled–program now in effect is an incredible waste.

Playboy: Ohio Senator John Glenn, who was one of our nation’s first astronauts, points out that the money question is easy to answer: Every dollar we put into the space program gives us seven dollars’ worth of new technology. He cites ten thousand medical devices and programs we have because of the space program.

Sagan: That has been one of the justifications offered since Apollo. Two items widely touted as examples of what we got from Apollo were the stickless frying pan and the cardiac pacemaker. In actuality, Teflon was invented in the Thirties and had nothing to do with the space program–a fact that Du Pont will be very quick to confirm. Also, I met the inventor of the cardiac pacemaker, who almost had a heart attack himself discussing the claim that Apollo had anything to do with his invention.

Still, suppose that weren’t right. Suppose stickless frying pans, in fact, emerged from the Apollo program. What is the argument? Give us seventy-five billion dollars to send people to the moon and we’ll throw in a stickless frying pan for free? If we’re into stickless frying pans, let’s spend whatever it takes to get a stickless frying pan. Why go to the moon in the process?

Playboy: Of the fourteen billion dollars budgeted for space exploration, how much goes to the manned program?

Sagan: Well over half. And what’s the real reason we send people?

Playboy: Economics–or, as they said in The Right Stuff, no Buck Rogers, no bucks.

Sagan: Right. That’s a prevailing prejudice in NASA, in the Executive branch and in some parts of the legislative branch. I don’t know if it’s true or not–and criticizing the manned, and womaned, space program may be killing the goose that lays the golden eggs–but this is a view that is contemptuous of the intelligence of the American public.

Playboy: What will the Gulf war–with its prolific use of Patriots and other antimissile missiles–mean for American technology in space; specifically, the Strategic Defense Initiative? Did it give more credibility to S.D.I.?

Sagan: There’s no question that some people think the Patriots demonstrated the utility and importance of Star Wars, even though Patriots were not developed in the S.D.I. program. But beyond that, some recent testimony by experts such as Theodore Postel of MIT suggests that they were very ineffective in shooting down the Scuds; actually, they may have killed more people than if the Scuds had gotten clean hits each time. Regardless, even if you thought that the Patriots had done a perfect job, that doesn’t say anything about how good you would be at shooting down a volley of intercontinental ballistic missiles.

The biggest effect of all the attention to military technology in the war is that now every tinhorn dictator in the world is going to want to have lots more smart weapons–more of that wonderful American technology that was so stimulatingly displayed on world television. That may be its most dangerous consequence. What’s more, vast resources for many nations will have to be spent on these exceptionally expensive weapons instead of on the national economies. And who’s going to sell it all? The United States.

Another way to look at the war is that it was a massive arms bazaar arranged by the United States to showcase some of the products that you, too, might acquire–and only for all the critical resources of your society that might otherwise be spent on bettering your people. Line up over here!

Playboy: Advertised for free on CNN.

Sagan: Which gets directly to the national leadership of all of those nations. If I’m sitting in Burundi or Nepal or El Salvador, to take three very different countries, and I’m a military officer, I think, Gee, it would be wonderful to have some of that stuff. What I could do with that! Other nations wouldn’t be able to push me around anymore! So what if the people have a little less?

Playboy: Getting back to S.D.I., what are your primary objections to it?

Sagan: Its purpose keeps changing. Ronald Reagan’s original justification, as sold to him by Edward Teller and others, was that it would provide a kind of complete protection for the citizens of the United States against a Soviet attack. Well, that was quickly modified; even the S.D.I. scientists admit that the protection couldn’t be complete. But even if the system were ninety percent effective–which no one thinks it could be–and the Soviets launched, let’s say, ten thousand warheads, and we shot down ninety percent of them–a thousand warheads would still get through. A thousand nuclear explosions on American soil is enough to destroy the United States many times over. Star Wars is a delusion.

Playboy: Some say S.D.I. could also destroy the possibility of a limited nuclear war. If we used it to shoot down a missile or two, for example, the enemy would feel it would have to launch thousands.

Sagan: That’s it. You shoot your wad in order to guarantee overwhelming the American defense system.

Playboy: But another argument is that S.D.I. enhances deterrence.

Sagan: Maybe a much better way to disarm the Soviets’ ability to destroy you is to have a treaty that destroys lots of their weapons. Star Wars is a technology desperately seeking a justification.

Playboy: Has the end of the Cold War slowed down the scientists who are building nuclear bombs?

Sagan: No. We and the Soviets are still building nuclear weapons every day.

Playboy: Bigger and better?

Sagan: At least better. New kinds of weapons–weapons that can burrow and kill people hiding in subways. All sorts of wonderful new inventions. There are a lot of bright people who are dedicated to their tasks and are doing rather well for themselves working on nuclear weapons. They are all convinced–or at least they were the last time I talked with them–that what they’re doing is patriotic and in the national interest.

Playboy: Physicist Ted Taylor built some of our most powerful bombs before becoming an advocate of complete disarmament; he worked twenty years before it dawned on him that his bombs might actually kill people. If you had your way, would you eliminate all nuclear weapons, as Taylor would?

Sagan: No. Getting down to zero, at least with the world the way it is today, is just too dangerous. Then somebody who had a handful could extort on a grand scale. A lot of people I admire don’t agree with me. I’m not a hundred percent sure I’m right, but my sense is, you need a minimum deterrent. Yet it can be at much, much lower levels than anything we have now. Fifty weapons could destroy any country on earth.

Playboy: Is that a realistic goal?

Sagan: Who knows what’s realistic? Was the dissolution of the Warsaw Pact realistic ten years ago? The world is changing at a phenomenal pace.

Sagan: I.N.F. did not reduce the world’s nuclear arsenals by one weapon; it merely destroyed the delivery systems. Our warheads were brought back to the United States and reconfigured into new nuclear weapons on new delivery systems. As for START, the number of deployed, operational warheads in the world would be reduced to the low forty thousands from something like fifty-five thousand. It is an obscene number–and still no warheads would be destroyed. What we need to do is get down to numbers that can’t trigger nuclear winter.

Playboy: Let’s move to that. How did you arrive at your nuclear-winter theory?

Sagan: The starting point was NASA’s Mariner Nine mission to Mars; it was the first spacecraft to orbit another planet. Instead of all the wonders that we thought we would find on Mars, once we got there, we saw a featureless planet covered by a global dust storm. An infrared spectrometer and radiometer measured temperatures in the atmosphere and on the surface, and we discovered that the atmosphere was much warmer and the surface much colder than they ought to be. It didn’t take a lot of insight to recognize that the dust storm was probably the cause. When it finally cleared, the wonders of Mars were revealed to us. So we forgot about the dust and didn’t look back at it for a few years.

When we did look back, it was when my colleagues and I were studying the climatic effects of large volcanic explosions on the earth. We did some calculations and noted similarities between the temperature drops following major volcanic explosions here and the dust-storm temperature drops on Mars.

The next thing that happened was related to Luis Alvarez’ discovery of the iridium layer around the earth. It—-

Playboy: Back up. Alvarez? Iridium?

Sagan: OK. Normally, there isn’t much of the metallic element iridium on the earth’s surface–that is, when compared with meteorites, asteroids and, presumably, comets. Luis Alvarez and his colleagues examined the sediments near what was the earth’s surface at the time of the extinction of the dinosaurs. He discovered that there had been a huge amount of iridium all over the world at that time. The assumption is that the iridium is a geological signature of an impact by an extraterrestrial body that was, according to the calculations, an asteroid ten kilometers across. It is now the most accepted theory that the asteroid hit the earth and scattered a dust cloud including iridium into the atmosphere, which eventually settled onto the earth. Temperature drops caused by the dust-cloud layer–like the temperature drops caused by the Mars dust storms and the volcanoes, but far worse–seem to be what caused the extinction of the dinosaurs. Later, I suggested that we take a look at what would happen in the atmosphere after a nuclear war using those climate models. Because of the questions about dinosaur extinction, the Department of Defense got interested as well.

Playboy: Why was the Department of Defense interested in the dinosaurs?

Sagan: It wanted to know if the climatic effects resulting from the catastrophe that destroyed most of the species of life on earth sixty-five million years ago could be caused by the ground bursts of nuclear weapons.

Playboy: What causes the dust in a nuclear explosion?

Sagan: An explosion excavates a giant crater, pulverizes the stuff and shoots it up into the skies. Scientists Paul Crutzen and John Birks have suggested that there would be another component far greater than the dust: soot caused by a nuclear war. None of our initial calculations considered the burning that would occur after a nuclear war–particularly of cities, which are made of very burnable stuff.

Playboy: So the final calculation combined the effects of the dust and the emissions from fires?

Sagan: That’s right. Essentially, the dust and soot would envelop the earth at a very high altitude, darken it and cause a devastating drop in temperature, below the temperature of the planet during the last ice age. That is nuclear winter.

Playboy: But wouldn’t a nuclear war destroy so much that concern about the aftermath is, frankly, irrelevant?

Sagan: The number of people who would be killed by the prompt effects–the blast, the radiation, the immediate fallout, the fires–are, indeed, so many, and the deaths so horrible, that you might think: Anything more than that, who cares? A lot of people have that view, but most of those people are living in the northern middle-latitude target zones. They would be killed–promptly, of course. However, people living in places that would not be targeted consider nuclear winter an important point. Nuclear winter is a way for nuclear weapons to kill people who don’t live in American, Soviet, European and Chinese cities. It is a way for nuclear weapons to kill everybody.

Playboy: Your argument points to the fact that there could be a limited nuclear war, and that’s the premise espoused by nuclear-war proponents.

Sagan: What they meant when they said limited nuclear war was that nations with twenty-five thousand nuclear weapons would be able to have a nuclear war and use only a few dozen each. That is absurd. The losing side would up the ante. It always does. Warring countries would stop using nuclear weapons only when there were no more left. The only experience we have had with that was in 1945, when the United States used its entire nuclear arsenal–both weapons.

Playboy: Are we less threatened now that we’re talking with the Soviets?

Sagan: I think we face a different set of dangers. The day-to-day tension between the United States and the Soviet Union has gone way down. The fear that the Soviets would make a massive armored attack across the Elbe into western Europe is completely dissipated. And we do have a much less nuclear-confrontationalist group running this country than we did in Reagan’s first term. In all those respects, things really are better. But you can’t say that if there’s no nuclear war in the next two or three years, we have nothing to worry about. There will be new nuclear-weapons states. And there will be new leaders, military and civilian–leaders who go crazy.

Playboy: Which is more threatening, a small country with weapons or a terrorist with a bomb?

Sagan: Look at what one weapon can do versus what a hundred can do versus what a thousand can do. It’s very clear that the biggest danger, in terms of both prompt and long-term effects, is from the nations that have hundreds or more.

Playboy: Do the officials who would make the decision to use nuclear weapons consider nuclear winter a serious deterrent?

Sagan: It’s hard to know. In the Soviet Union, the answer seems to be yes. How seriously it is taken in the United States is unclear. In the Reagan years, nuclear winter was considered a dangerous idea, because it might make Americans think that nuclear war was foolish. Our deterrence of the Soviet Union depended on having a credible threat.

Playboy: With whom in the current Administration have you discussed this?

Sagan: Over the years, I’ve talked with the State Department, the Department of Defense, the Central Intelligence Agency and even the National Security Agency.

Playboy: And do they accept the theory?

Sagan: There are those who do and those who don’t. I was asked to talk in a lot of forums about it. I can’t complain that the whole thing was stiff-armed, that nobody wanted to hear it. I know of cases in which high Government officials were hiding behind a one-way mirror when they were being briefed on nuclear winter. The scientists did not know which officials might be hiding behind the glass; the officials were unwilling to have it publicly known that they had heard something about nuclear winter.

Playboy: What did the Department of Defense do with the information you provided?

Sagan: People high in the department were appalled at the ideological implications of nuclear winter; others thought we were exaggerating; a few thought we were minimizing.

Playboy: In general, have you found military leaders to have much scientific understanding?

Sagan: It’s hard to make generalizations. My anecdotal impression is that the professional, high-ranking military officers were much more open to nuclear winter than the ideologically oriented civilian political appointees. In my experience over the past twenty-five years with the Department of Defense, I have found that the willingness to consider new ideas is much greater than you’d expect from the stereotype of the closed military mind. Or maybe they just have a better tradition of politeness. But ideological civilians don’t want to hear things that might affect their politics. In the DOD, some right-wingers have accused us of having invented nuclear winter in order to accomplish the nuclear freeze or to prevent the installation of Pershing Twos and cruise missiles in Europe. Some people were afraid of the truth–afraid that knowledge of a much worse, long-term consequence of nuclear war had unacceptable political implications–and so maybe we should pretend that this evidence didn’t exist or was mistaken.

Playboy: How would a nuclear war affect the ozone layer?

Sagan: The ozone layer would be severely affected by a nuclear war–and not just by the oxides of nitrogen that rise into the stratosphere in the fireball but by the soot itself. Calculations at Los Alamos National Laboratory show that there would be a very serious depletion of the ozone layer–one that hadn’t been anticipated before. You’d take your life in your hands going for a walk–which is only a slight exaggeration.

Playboy: For the confused, explain the ozone problem.

Sagan: There is a thin layer that protects us from ultraviolet radiation from the sun. The gas, ozone, is transparent and invisible–we can look out in ordinary visible light and see stars–but is opaque to ultraviolet light. When we deplete the ozone layer, excessive ultraviolet light gets in. There are many dangerous consequences. Skin cancer in light-skinned people goes up, as do cataracts. The immune system is attacked, kind of like AIDS, except you don’t have to do anything special to get it. Most serious and least understood is the fact that the primary photosynthetic producers–such as the phytoplankton in the oceans–are vulnerable to ultraviolet light. You kill those guys, you kill everybody above them in the food chain.

Playboy: A report recently released by the Government said that the ozone depletion around the earth is far worse than previously predicted.

Sagan: Right. And notice what “far worse” is? Far worse means that there has been a few-percent depletion at northern mid-latitudes, where most Americans live, whereas in the nuclear-winter scenario, it’s say, thirty times worse.

Playboy: Do most people take the threat seriously?

Sagan: Many of us take it very seriously. Almost all of the industrialized nations have agreed to phase out the chlorofluorocarbons [CFCs], which are the worst enemy of the ozone layer. But molecules of CFC, which are released by air conditioning and refrigerators, continue to do damage to the ozone layer for what will be the next hundred years.

Playboy: While we’re on the good news, explain the greenhouse effect.

Sagan: While ozone absorbs radiation in the ultraviolet, the greenhouse effect works in the infrared–that’s wave lengths of light longer than visible light. In ordinary visible light, the atmosphere is transparent, except in Los Angeles and Denver and a few places like that. The earth tries to cool itself by radiating to space in the infrared. Now, because of carbon dioxide and other gases, the atmosphere is fairly opaque in the infrared. Consequently, the heat can’t get out and the temperature rises. Just like how a greenhouse is supposed to work.

Playboy: How does the damage from chlorofluorocarbons compare with the damage from CO2 emissions?

Sagan: The CFC industry in the United States was a six-hundred-million-dollar-a-year industry. That’s a lot, but compared with the U.S. economy, it’s trivial. Whereas if you’re seriously talking about phasing out a significant fraction of the fossil-fuel industry, you are taking on the coal, oil, gas, auto and chemical industries. That’s much tougher than taking on a six-hundred-million-dollar industry.

Playboy: Of the two–CFCs and CO2–which is the more significant problem?

Sagan: It depends on which you think is more dangerous–ozone depletion or global warming. Who knows? [Laughs] But our reaction shouldn’t be, “We can solve only one of these problems, so which will it be?” We must solve both–they’re both extremely perilous.

Playboy: Part of the debate is over whether or not the greenhouse effect is actually occurring.

Sagan: The six warmest years of the Twentieth Century were in the decade ending in 1990.

Playboy: Do you attribute that to global warming?

Sagan: It is impossible to know for sure, but it seems a good bet. At least ignoring it looks to be imprudent.

Playboy: Is global warming also responsible for the recent drought in the Midwest and the West?

Sagan: It’s a riskier step to draw that conclusion. The question is, do we have the signature of global warming? Some very capable scientists say yes, though some say no, not yet.

Playboy: How can we expect governments to react?

Sagan: It’s a question of how cautious you want to be. On the one hand, if scientists make some pronouncement about a danger–and nations take precautionary action that’s expensive–and then it turns out that the scientists were wrong, then we’ve wasted a lot of money and the scientists are in trouble. Some scientists say that you have to be certain that it’s happening before you speak out. But in my view, even if we take steps to stop global warming by burning fossil fuels more efficiently and coming up with fossil-fuel alternatives, and then find out that every scientist who had worried about it was just dead wrong, we’d still have helped ourselves. It would help end our pernicious dependence on foreign petroleum. It would help solve the problem of oil spills. Also, a lot of acid rain is connected with the burning of high-sulphur coal. We can solve many serious environmental and political problems by lessening our dependence on fossil fuels.

Playboy: Which fossil-fuel alternative do you consider the most viable?

Sagan: Solar electric power, wind turbines, biomass burning, hydrogen fuel. The principle of that last one is wonderful. It may work off of water and sunlight.

Playboy: What’s our country’s argument against hydrogen fuel?

Sagan: Cost–but it’s not a valid argument. For instance, what is the cost of a barrel of petroleum? Well, if we charge only the direct cost of the petroleum to the consumer, then we get a comparatively low figure, and it’s hard for hydrogen fuel or solar electricity to compete. But if we throw in the military cost of maintaining armed forces to protect our oil supplies, the cost of occasional excursions such as the Persian Gulf war, the environmental cost of cleaning up the damage, the medical cost of people’s breathing toxic fumes, the agricultural cost of dealing with global warming, the refugee cost, the cost of the sea level’s rising and low-lying cities’ being flooded–if we add all that to the cost of a barrel of oil, we’ll find that hydrogen fuel and solar electricity are cheaper by far. We just don’t do the accounting right. We cheat.

Playboy: Are the oil-well fires in Kuwait remaining from the war contributing to the greenhouse effect?

Sagan: Of course, but not in a major way. Still, no one has ever before burned five hundred oil wells at once; there is a nightmarish, hellish situation in Kuwait right now. The skies are darkened, temperatures are lower–five, ten degrees Fahrenheit lower than they ought to be for this time of year. These Mephistophelean flames are all over the landscape. That’s quite a vision of hell. It’s only one example of the formidable, maybe even awesome, technological powers we humans now have.

We keep discovering–by accident–the danger these things pose, yet the discoveries are never made by the industry that’s making money from the new technology. Who discovered that chlorofluorocarbons are a danger to the ozone layer? Was it Du Pont, a principal manufacturer, exercising corporate responsibility? No. Was it the Environmental Protection Agency, which is supposed to be protecting us? No. Was it the Department of Defense, which is supposed to be defending us? No. Then who was it? It was two white-coated ivory-tower scientists at the University of California Irvine–Sherwood Roland and Mario Molina are their names. They weren’t going after Du Pont or anything like that; they were simply interested in the photochemistry of the upper atmosphere.

Why were Roland and Molina the ones who discovered the problem? Why didn’t the industrialized nations make a concerted effortbeforehand to explore the dangers of the new technologies?

Playboy: Cost priorities, maybe?

Sagan: But in terms of the cost to the society, you save money by finding out the dangers early. So why is there no Governmental research institute, no Department of Citizen Protection, to seek these things out?

Playboy: As far as the oil-well fires are concerned, at least one report says that the pollution isn’t toxic.

Sagan: I have heard a lot of complaints about respiratory illnesses. People with asthma are leaving the country; respiratory wards in hospitals are oversubscribed. Also, there’s now the petroleum pollution of the Persian Gulf. We now have black rain–or black snow–as far away as the foothills of the Himalayas. All of that is going to have some serious consequences.

Playboy: How serious?

Sagan: The estimated time required for putting out the fires is something like two to five years. A lot can happen in two to five years. Much depends on the weather. One of the things that I’ve been most worried about is the possibility of the climatic consequences, not just over the region but extending to all of South Asia or beyond. It would require the soot to get up to very high altitudes. So far, very little of it has done so. If the stuff gets up to high altitudes, the climatic effects will be more serious and widespread.

Playboy: Could this fiasco result in a scaled-down version of nuclear winter?

Sagan: The worst-case scenario of the Kuwaiti oil fires doesn’t come near nuclear winter. However, nuclear winter is so serious that even something far short of it can do substantial damage. One of the ways that nuclear winter works is by partially turning off the greenhouse effect. That is, if soot blocks sunlight high up in the air, above where the bulk of the greenhouse gases are, then it doesn’t allow those gases to do their stuff. We need some greenhouse effect, just not much. The earth, without our present greenhouse effect, would be below the freezing point of water. The oceans would freeze. We’d be dead.

Playboy: One way we freeze, the other way we burn. Nice choices.

Sagan: [Smiles] Exactly.

Playboy: How much does President Bush listen to scientists?

Sagan: There is currently a Presidential science advisor, Allan Bromley, a distinguished physicist from Yale, but there is no evidence that Bush listens to scientists on anything that challenges policy. Bush is interested in science and the space program to accomplish very short-term political objectives, nothing else. It’s ironic, because, in the Soviet Union, Gorbachev has been close to a number of scientists, and I believe they have played a critical role in many of the changes that have occurred there.

The last U.S. President who had science advisors with a great deal of influence was Eisenhower, though Kennedy paid a lot of attention to his, as well. Carter had a very capable advisor, Frank Press, who’s now the president of the National Academy of Sciences; and Carter himself was personally very interested in science. Nixon actively ignored the scientists. One example was when his Administration, for political reasons, wanted the supersonic transport, but experts pointed out various deficiencies in its cost-effectiveness. So politics and science collided, as they often do, and Nixon’s response was to dissolve the entire Presidential science-advisory committee. That’s the thing about science. It’s completely unreliable politically–there’s no telling what nature will reveal.

Playboy: For one thing, experts often don’t agree.

Sagan: You can make any conclusion you want by finding the right scientist, and you’ve really got to concentrate to understand what they’re saying. But their advice is an iffy thing for Presidents and prime ministers and premiers, mostly because it cannot be controlled.

Playboy: Do most scientists have a sense of social responsibility?

Sagan: Some are just concerned with salaries and promotions. Many are unprepared for the rough-and-tumble, unscrupulous world of politics. Others don’t want to offend those in power; if you find something that’s contrary to the prevailing wisdom, it may be better not to mention it. Others don’t care about the prevailing politics–they just feel they should speak their conscience.

Playboy: Were you always political, or has your career politicized you?

Sagan: I grew up in the Depression. My parents were very poor, so I understood poverty and I understood what Government could do to help or hurt those who were poor. When I was born, my father was an usher in a movie theater, but things eventually got better for us. I was aware of politics, I suppose, but I never was political.

Playboy: Was your childhood unique?

Sagan: One very important thing was that my parents had a sense of the worth of knowledge–the value of learning just for fun. That was certainly communicated by both of them. They had a good command of the English language, there were books in the house. One of the things I’m most grateful to them for is that they did not discourage even my wildest flights of fancy. In the Forties–in the middle of World War Two–when I decided I was interested in being involved with sending rocket ships to the planets, they didn’t say, “Oh, come, on.”

Playboy: So, when you were a child, you knew what you wanted to do?

Sagan: I had questions. I’d ask bigger kids what the stars were and they’d say, “They’re lights in the sky, kid.” I knew they were lights in the sky–but what were they? My parents sent me to the library. Kids are naturally curious and want to understand about the world and they’re eager to learn. It’s only when they’re turned off by adults that they stop asking questions–which is why I put so much emphasis on the fact that my parents didn’t discourage me. When I discovered that there were such things as planets, I wanted to go to them. Then, when I was eight or nine, I came upon science fiction. These people were going to planets. I read loads of science fiction, especially Edgar Rice Burroughs’ John Carter series about a guy who gets to Mars by wishing hard. I spent a lot of time wishing at Mars hard. It didn’t do a thing.

Playboy: What were you like socially? Did you fit the stereotype of the awkward, nerdy kid interested in science?

Sagan: Well, certainly at the age of thirteen, I was awkward and perhaps nerdy, and that probably would have been the case no matter whatI was interested in. But by the time I was a junior or senior in high school, I had lots of friends and a steady girlfriend.

Still, kids interested in science are usually defined as uncool, which is a way for those who are uncomfortable with science to deal with it. It seems that those who are not very good at thinking, or those who haven’t been encouraged, have a vested interest in putting down the social importance of learning. You can see lots of peer pressure in high school not to excel in academics, but you never see peer pressure not to excel in sports. I think high schools ought to give letter jackets to students who are excellent academically, at least as much as to students who are excellent in sports.

Playboy: How do you encourage your kids?

Sagan: Are you kidding? They are unstoppable. When they ask questions, answer them. If you don’t know the answer, help them find it.

Playboy: You have children ranging in age from ten months to thirty-two years. How has being a parent affected you?

Sagan: Annie pointed out to me that I had one child per decade for the last five decades in the Twentieth Century. [Laughs] I think I get to be a better father each time. I hope so. And while I recognize that there are still lots of things I have to learn about being a parent, I have certainly enjoyed it from the beginning. It’s an opportunity to reach into the future a little bit. A parent has an awful lot to say about how a child turns out. And having children sews up all the various parts of your own life–if that makes any sense. You can’t spend time with a child of a certain age without getting back to yourself at that age. There’s a tendency to lose contact with the different parts of you as you grow up, the eight-year-old in you, for example–it’s childish and embarrassing. But it’s still there. When you have an eight-year-old, it all comes back, and you sort of reintegrate it into your personality. It’s a deep experience, and I think men in general don’t get nearly enough out of it.

Playboy: Getting back to your work, are people becoming more enlightened about environmental issues–celebrating Earth Day, recycling, that sort of thing?

Sagan: They are, except that there is what I call the brick-in-the-toilet problem. It’s very easy to tell people that they should work hard in their local communities to improve conditions: Put a brick in your toilet so the amount of water per flush is less, separate plastic from paper for recycling. I’m certainly for those things. But they tend to obscure the major environmental issues that cannot be solved by changes in individual behavior–global warming, say, or ozone depletion. The significant things that must be changed involve industrial and national policy, short-term profits versus the long-term well-being of the environment.

Playboy: Are bricks in the toilets trivial?

Sagan: No, but we have to do both. The danger is that people have a sense of satisfaction after they separate the paper and they forget about it; they think the problems are solved.

The tendency to solve the problems that you know how to solve is very human; but if that takes away from solving the most serious problems, there’s grave danger. All sorts of industries that might have reckless environmental policies are happy to encourage individuals to put bricks in their toilets. People in Detroit are happy to have people recycle bottles rather than insist on fuel-efficient automobiles. Having modern fluorescent lamps as opposed to incandescent ones is something General Electric ought to worry about, but it would rather have you pile up newspapers. Building solar-electric alternatives to fossil fuel is something that the Government should pay attention to in its tax-incentive and sales-tax-rebate policies.

Playboy: Wouldn’t the same people who put bricks in their toilets buy fuel-efficient cars and more efficient bulbs?

Sagan: Maybe. Detroit says no. G.E. says no. But public-opinion polls show that people would be willing to pay significantly more taxes if they were sure that those taxes would be spent ameliorating the environmental problems.

Playboy: Is it significant when a company such as McDonald’s succumbs to the country’s mood and begins recycling in its restaurants?

Sagan: Yes, but are they doing the significant things and not just things that the customers see? In other words, are they doing more than just PR?

Playboy: Do we have the technology to solve the environmental problems?

Sagan: Absolutely. It’s a question of having the political will.

Playboy: What would it take to change?

Sagan: Imagine freeing up a significant amount of the Department of Defense’s scientific and engineering talent–away from weapons and toward solving these problems.

Playboy: So it’s money. But can Detroit make fuel-efficient cars at prices that Americans will pay?

Sagan: When Detroit auto makers were arguing against compact cars, they said it was impossible, that it would bankrupt them; they’d have to have all sorts of new assembly lines and no one would buy compact cars. The Japanese, despite all that, made comparatively inexpensive, excellent compact cars, and suddenly Detroit was able to find the resources.

I think the problem is that a large initial investment is needed to make any major change. The auto industry is already in such trouble that it doesn’t have the resources to make the initial investment. So it finds arguments about why not to change. Putting in an air bag is considered a huge step forward; the auto industry touts it in its advertising as if it were done for humanitarian, philanthropic reasons. Whereas making major changes of the sort necessary to deal responsibly with global warming and energy independence–well, you don’t see much of that.

Playboy: So what would you have them do in Detroit?

Sagan: There are already fifty-mile-a-gallon cars in Japan. That’s the first thing Detroit should do. They claim it won’t be as safe. So make it safe. They’ll be forced to go in that direction, anyway. Detroit will be huffing and puffing after the Japanese or the Koreans or whoever it is.

Playboy: It seems that everybody can read the writing on the wall. Why, then, don’t the oil companies invest in liquid hydrogen or other new technologies–if for nothing else, to maintain their monopolies on fuel?

Sagan: When the first autos came along, wouldn’t it have made sense for the blacksmiths to see the writing on the wall and throw away their hammers, anvils and horseshoes and go into selling used cars? But they didn’t, because they knew about the blacksmith profession, they saw virtues in horses that they didn’t see in autos and they wouldn’t have to learn a whole new technology.

Playboy: Still, it’s hard to believe that the people responsible for the billion-dollar industries aren’t looking ahead.

Sagan: Look at the board-room-turnover rate in this country. How long do corporate executives stay with their particular companies? Is it long enough for a long-term investment to pay off for them personally? No. They’re gone in three to five years, while the long-term investment reaps rewards in ten or even twenty years. It’s not to their advantage in terms of salary, bonuses, stock options–their personal motives–to do it. Executives in Japan often stay with their corporations for life and can make long-term plans. Could that be a reason Japan’s industries are so much healthier than ours? I think it is.

Playboy: So perhaps the next innovations–the first liquid-hydrogen cars, say–will come not from the big corporations but from young entrepreneurs.

Sagan: Young Japanese or Korean or Singaporean or Hungarian entrepreneurs, because there’s just not much sign that it’s happening in America. And it’s not going to get better any time soon. Beyond the lack of motivation of the big companies, the declining level of technical competence in America is another reason we probably won’t come up with the inventions.

Playboy: Is better education the solution to that?

Sagan: Yes, but look at the time scale again: Make the investment in education now and we don’t see the benefit for twenty years at the earliest. Does any company care about what happens twenty years from now? Is it willing to forgo profits and dividends now so that there will be more profits and dividends twenty years from now? Is corporate America designed for this kind of thing? Are American politicians concerned about twenty years down the road?

Playboy: What’s the likely scenario?

Sagan: It’s a Darwinian scenario: The countries that can figure out what to do will prosper, and those that can’t won’t.

Playboy: Doesn’t this sort of get to you sometimes–the greenhouse effect, ozone depletion, acid rain, not to mention nuclear winter? Don’t you ever get tired of being the doomsayer?

Sagan: Well, I personally find it so much more fun to be pursuing science and understanding how the world works and exploring the mysteries of other planets than constantly calling attention to dangers. There’s a grumpy quality about all these jeremiads; I don’t in the least bit enjoy it. But if I’m aware of a danger that requires public attention, I have a responsibility to speak out.

Playboy: There’s such a thing as overload, though. Don’t people sometimes just turn you off because the problems seem too big and too dangerous?

Sagan: Well, suppose it’s decades in the future and we’re actually in the grips of some monstrous environmental disaster, and then I have to look back on my conduct. Which is better–to say I warned of this but people paid no attention because they couldn’t bear to grapple with all the unpleasant things going on, or that I kept quiet for fear of bothering people? In which case would I feel that I had fulfilled my obligation to my children, my grandchildren? The answer is clear.

Playboy: But instead of facing the problems, some people just want to close their eyes to them.

Sagan: Psychologists have a word for that. Denial. [Looks up, smiles] And as the Dire Straits song goes, “Denial ain’t just a river in Egypt….” [Sagan gets up to leave; he's expected at Cornell's Space Science building.]

Playboy: Oh, wait–one more thing: Why is the sky blue?

Sagan: [Laughs] I asked for it. OK. [Sits back down, takes a deep breath] Light comes in waves from the sun and those waves have different lengths. The shorter wave lengths show up to the naked eye as violet, then, going to longer wave lengths, blue, and on through green, yellow, orange and red. That’s called the spectrum. The molecules that make up the air are very small, and as it turns out, the shorter light waves are bounced back by these molecules better than the longer ones. When the sun is coming straight at you, a lot of the blue light is bounced away and scatters off into the rest of the sky, which then looks blue. When the sun sets, the light has a longer path to travel than when it was directly overhead; the blue light is scattered out of the beam, so the sun appears red. The blue sky and the red sunset are sort of the plus and the minus of the same phenomenon.

Playboy: And why is the sun yellow?

Sagan: That’s also connected to the spectrum. The wave lengths of light that hot things give off tend to move from the longer red to the shorter blue as the emitting source gets hotter. Take a poker and put it into the fire. When it starts to glow, it’s red–red-hot, as we call it. If we continue to heat it, it emits light farther and farther into the blue, and it begins to get white–white-hot. Similarly, a cool star will look mainly red; a very hot star will have a bluish tinge to it. And a star whose surface temperature is intermediate–like our sun–will look yellow.

Playboy: Finally, what is a dream?

Sagan: We still don’t know–which is amazing when you consider how pervasive dreaming is in the lives of every human being. Maybe dreams are just the processing of the day’s data; maybe they’re the expression of deeply powerful emotions that we, as Freud suggested, don’t have the courage to face in our waking lives–so we have to disguise them; and maybe they have no meaning whatsoever, and they’re merely the brain’s computer programs straightening everything out at nighttime. We simply do not know the answer.

But if a kid asked me that question, I would say this: Maybe, when you grow up, you‘ll find the answer.

David Sheff is a journalist and New York Timesbest-selling author. His latest book Clean was published in April 2013.